Usually, a touch input device is an input device attached onto or incorporated in a display device such as LCD (Liquid Crystal Display), PDP (Plasma Display Panel), OLED (Organic Light Emitting Diode), and AMOLED (Active Matrix Organic Light Emitting Diode) and detects a touch signal corresponding to a touch point as an input signal when an object such as a finger or pen contacts the touch input device. The touch input device is very widely used for mobile devices such as mobile phones, PDA (Personal Digital Assistant), and PDP (Portable Multimedia Player). Besides, the touch input device is also applied to a large-sized video display device such as monitors and TVs.
The touch input device generates an input signal corresponding to a coordinate of a touch point when a touch input occurs at least one selectable area among a plurality of selectable areas that are usually displayed as graphic images on a touch panel. For example, if graphic images such as icons or keypads provided on a screen of a display device are touched, input signals that correspond to the selected icons or keypads are generated.
As described above, in the case that graphic images such as icons or keypads are displayed on a screen, background images overlap with the graphic images such as icons or keypads for touch inputs. As a result, the background images may deteriorate. In addition, there is a problem that touch inputs may become complicated since graphic images such as icons or keypads for touch inputs should be activated.
For example, a method of detecting a zoom gesture in a conventional touch panel includes the steps of activating icons for inputting the zoom gesture, touching a corresponding icon, and generating a zoom-in or zoom-out signal in correspondence to the input icon. In addition, when a zoom gesture is ended, a user should close icons for the zoom gesture again. This zoom gesture realization method has problems that background images overlap with the graphic images such as icons or keypads for touch inputs as described above, GUI (Graphical User Interface) for a zoom gesture should be provided separately, and user's touch inputs become complicated.
In addition, a conventional zoom gesture detection method has a problem that it is difficult to select an area to be expanded or reduced on a screen. In most cases, an area to be expanded or reduced on a screen should be selected, or cannot be selected in advance, prior to starting a zoom gesture.